Hermetically-sealed thermostat



. July 25, 1950 B. F. PARR 2,516,584

HERMETICALLY-SEALED THERMOSTAT Filed Jan. 18, 1947 FIG.Z.

WITNESSES: INVENTOR BERNARD F. FARR ATTORNEY Patented July 25, I950 HERMETICALLY-SEALED THERMOSTAT Bernard F. Parr, Mansfield, Ohio, minor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 18, 1947, Serial him 722,851 2 Claims. (Cl. 200-138) My invention relates tothermostats, more par- ,ticularly to thermostats which are sealed within fluid-tight casings, and has for an object to provide an improved thermostat of this kind.

A further object of my invention is to provide an improved hermetically-sealed thermostat for use with electrically-heated bed coverings, pads,

uniforms and the like for preventing overheating thereof.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawing, forming a part of this application, in which:

Fig. l is a view, partially in section and partially in elevation, of a thermostat constructed in accordance with my invention; and

Figs. 2 and 3 are, respectively, plan and end views of the thermostat shown in Fig. 1.

Reference will now be had to the drawing wherein I have shown an embodiment of my invention which is particularly adaptable for attachment to electrically-heated bed coverings, pads or uniforms, and which functions to prevent the overheating thereof. As apparatus of this kind is washed or dry cleaned periodically, it is desirable that the safety thermostats controlling their heating elementsbe isolated from the cleaning or washing fluid in order to prevent damage to the thermostat or the accumulation of cleaning fluid around the thermostat. The thermostatically-operated switch structure is generally indicated at ill and may include a frame ll having a stationary contact [-2 fixed thereto and a movable contact [3 carried by a resilient support l4 and cooperating with the stationary contact l2. The resilient support is insulated from the frame H in any well-understood manner and a bimetallic member l5 having its high expansive metal uppermost is also carried by the frame l0 and functions to disengage the contacts l2 and I3 in response to a predetermined high temperature. Terminals l6 and Il are electrically connected, respectively, to the frame I ll and the spring support H and conductors l8 and I 9 are soldered or otherwise secured to the respective terminals l6 and H. The conductors i8 and I! may be electrically connected to the heating element of the apparatus (not shown) being controlled, or these conductors may be extensions of the heating element.

In accordance with my invention, the thermostatically-operated switch in is arranged within a relatively rigid housing 2| which may, for example, be formed of fiber tubing. An elongated 2 tubular shell 22 surrounds the tubular housing 2| and is somewhat longer than the housing 2| so that its ends are spaced outwardly from the ends of the housing 2|. The insulating covering of the conductors i8 and I9 and the shell 22 are formed from thermoplastic material such as, for example, plasticized polyvinyl chloride. As shown, the ends of the shell 22 are crimped flat to close the ends of the shell 22 and to engage the insulation of the conductors l8 and IS. The crimping or flattening of the ends of the shells 22 may be effected in any well-understood manner such as, for example, by a pair of dies (not shown) which are heated during the flattening process sufficiently to cause the thermoplastic material of the shell and the insulation of the conductors i8 and 19 to flow and form an autogenous connection which is fluid-tight. Accordingly, the shell 22 defines a hermetic casing in which the thermostat i0 is enclosed. Preferably, the thicknes of the insulation of the conductors f8 and i9 is increased at the points where the shell is connected thereto, as shown at 20, in order to provide additional material for forming the autogenous connection and to insure that the conductors will not be damaged by the dies during the sealing step just described.

Preferably, before sealing the ends of the shell 22, the conductors i8 and I9 are bent slightly, as shown at 23 and 24, in order to relieve any strain on the terminals l6 and ll during the sealing-in process. Furthermore, the bends in the conductor also prevent the straining of the conductor or the terminals I6 and I1 if the ends of the shell 22 are bent in service, it being understood that a thermoplastic material, such as polyvinyl chloride, is relatively pliable.

From the foregoing description, it will be apparent that I have provided an improved hermetically-sealed thermostat structure havin a thermoplastic casing connected autogenously to the insulation of the conductors extending therefrom. While I have described polyvinyl chloride as the preferred material for the shell, it will be understood that other thermoplastics may be employed. Furthermore, the rigid housing which encloses the switch effectively protects the switch from extraneous forces to which the structure may be subjected. The provision of a bend or additional length in the conductors between the autogenous seal with the shell and the switch structure prevents straining of the conductors or the switch terminals to which they are connected in the event that the ends of the shell are bent or distorted in service.

While I have shown my invention in but one form. it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof.

What I claim is:

'1. In a hermetically-sealed thermostat structure, the combination of a thermostatically-actuated switch mechanism having a pair of terminals, a pair of conductors secured respectively to the terminals and having an insulating pliable thermoplastic covering, a relatively stiff housing surrounding the thermostatically-actuated switch mechanism and an elongated tubular thermoplastic shell surrounding said housing and having its ends spaced outwardly from the ends of the housing, said conductors extending outwardly through the respective ends of the thermoplastic shell, said ends 01' the thermoplastic shell being crimped to engage the thermoplastic covering 01' the respective conductors and heat treated to close the ends of the thermoplastic shell and to seal the same to the coverings of the conductors, said cone ductors having respective bends formed therein intermediate said terminals and the portions of the conductors which are sealed to said shell.

2. The combination as claimed in claim 1 wherein said shell and covering for the conductors are formed of plasticized polyvinyl chloride.

BERNARD F. FARR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'IENTS Number Name Date 1,851,657 Appelberg Mar. 29, 1932 2,018,512 DeLaney et al. Oct. 22, 1935 2,020,538 Denison Nov. 12, 1935 2,240,625 Fitzmaurice May 6, 1941 2,255,187 Reasoner Sept. 9, 1941 2,320,811 Cook June 1, 1943 FOREIGN PATENTS Number Country Date Great Britain May 21,1935 

